ST-HL-AE-3007, Special Rept:Loose Parts Monitoring Sys (Lpms) Channels 3 & 4 Inoperable for 30 Days Due to Inadequate Acoustical Coupling to Head.Caused by Design Error in Selection of Sensor Mounting Location

Special Rept:Loose Parts Monitoring Sys (Lpms) Channels 3 & 4 Inoperable for 30 Days Due to Inadequate Acoustical Coupling to Head.Caused by Design Error in Selection of Sensor Mounting Location

ML20235Z123
Person / Time
Site:	South Texas
Issue date:	03/02/1989
From:	Vaughn G HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3007, NUDOCS 8903150171
Download: ML20235Z123 (3)

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1. . The Light companyS uth Texas Project Dectric GeneratingP.Station O. Box 289 Wadsworth, Texas 77483 llouston Lighting & Power March 2, 1989 ST-HL-AE-3007 File No.. G26 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 Inoperable Loose Parts Monitoring System Channels Pursuant to the South Texas Project Electric Generating Station FSAR Section 4.4.6.4, Houston Lighting and Power submits the attached Special Report regarding inoperable loose parts monitoring system channels.

If you should have any questions on this matter, please contact Mr.

A. Harrison at (512) 972-7298.

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y G. E. Vaughn Vice President Nuclear Plant Operations GEV/ RAH /hg

Attachment:

Special Report Regarding Inoperable Loose Parts Monitoring System Channels l

l 8903150171 890302 PDR S

ADOCK 05000498 PDC 1 L4/NRC/EG.

A Subsidiary of Houston Industries Incorporated I \

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Attachmsnt 1 .

. ST-HL-AE-3007 J :I File No.: G26 Page 1.of 1 Special Report Regarding Inoperable k Loose Parts Monitoring System Channels Description of Event:

l Loose Part's Monitoring System (LPMS) channels 3'and 4 have~been inoperable for 30. days at the South Texas ~ Project (STP) Unit 1. In accordance with the STP FSAR and Regulatory. Guide 1.133, a special report to'the.NRC Regional' Administrator is required when one or more LPMS channels are inoperable for greater than 30 days. The inoperable LPMS channels monitor for

loose parts in'the reactor-vessel head.

During recent calibration and troubleshooting of the LPMS, it'was discovered that the two sensors mounted in the reactor vessel closure head

. area did not have adequate acoustical coupling to the head. This results in these two sensors not being sensitive to a loose part in the upper head region.

The present design.of the sensors is to attach the accelerometers to a bracket welded to the shroud cooling duct support ring. This ring is supported and bolted to the head in four. locations. This attachment does not provide adequate acoustical coupling to the head. The present design was tested'in the past by impacting the shroud cooling duct support' ring instead of the closure head itself. This test method made the system appear to meet specifications for sensitivity.

Safety Consequences:

No credit is taken for the LPMS in accident analyses nor does it serve as safety-related protection feature. However, HL&P believes'an operable LPMS is desirable for reliable plant operation and plans to correct the condition.

Root Cause:

The root cause appears to be a design error in the selection of the sensor mounting location.

Corrective Actions:

The other LPMS sensors at the remaining locations (i.e. bottom of reactor vessel and bottom of steam generators) have been determined by test to be adequately acoustically coupled.

Preliminary design is in process for relocating the affected reactor vessel head sensors The LPMS design for STP Unit 1 and Unit 2 are identical and similar corrective actions will be taken. HL&P will correct this condition at the first refueling of each unit.

L4/NRC/EG.

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E-3 1 Houston Lighting & Power Company '

d.T. South Texas Project Electric Generating Station -  !

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-1 Regional-Administrator, Region IV Rufus S. Scott .

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' Nuclear Regulatory Commission Associate'Ceneral Counsel _

l 611tRyan Plaza Drive, Suite 1000 ' Houston Lighting 6. Power Company Arlington,jTX ;76011-- P.~.O. Box 1700L Houston, TX -77001- j George Dick, Project Manager- 1

'U.S.

. Nuclear Regulatory Commission

INPO  !

Washington,1.DC 20555- Records' Center .

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~1100 circle'75 Parkway. .

' Jack E.: Bess .

Atlanta, GA :30339-3064- ];

Senior Resident Inspector / Unit 1 c/o U.S. Nuclear: Regulatory '

Dr. Joseph.M. Hendrie l

, Commission- 50 Bellport Lane l P. O. Box 910' Bellport, NY;:11713 ,

1 Bay; City, TX 77414  ;

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'J. I. Tapia l' Senior Resident Inspector / Unit 2' c/o U.S. Nuclear, Regulatory.

Commission P. O. Box 910 Bay City, TX- 77414-J.:R..-Newman, Esquire .

Newman & Holtzinger, P.C. )

1615 L Street, N.W.

. Washington, DC 20036 l J

R..L. Range /R. P. Verret  !

Central Power &. Light Company ,j P. O. Box 2121 1 Corpus Christi, TX 78403 l R. John' Miner (2. copies) R

' Chief Operating Officer. j City of Austin Electric Utility 7211 Barton Springs Road Austin, TX 78704 R. J. Costello/M..T. Hardt City Public Service Board P. O. Box 1771 San Antonio, TX .78296 l

1 Revised 12/21/88 L4/NRC/EG.

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